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sched_ext: Fixes for v7.3-rc4

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- A task reenqueued while its dispatch was still completing had its queued
   state clobbered by the dispatcher, dropping every later dispatch of the
   task. Wait for the in-flight dispatch to settle first.
 
 - A wakeup activation on another CPU marked the destination runqueue as
   mid-wakeup, stranding a pending local reenqueue. If the scheduler was
   unloaded first, the stale request pointed into freed memory that the next
   scheduler dereferenced.
 
 - ops.dequeue() ran with the source dispatch queue's lock held, so a
   scheduler iterating that queue from the callback deadlocked the CPU.
 
 - Schedulers with their own CPU ID mapping had no way to learn a task's
   initial CPU mask and rebuilt it themselves, which went wrong across
   sub-scheduler enable and re-home. Pass it to ops.enable().
 
 - A bypass dispatch event counter missed the dispatches made by the
   end-of-dispatch fallback and under-reported.
 
 - Selftests for the dequeue locking and initial mask changes.
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Merge tag 'sched_ext-for-7.3-rc4-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext

Pull sched_ext fixes from Tejun Heo:

 - A task reenqueued while its dispatch was still completing had its
   queued state clobbered by the dispatcher, dropping every later
   dispatch of the task. Wait for the in-flight dispatch to settle
   first

 - A wakeup activation on another CPU marked the destination runqueue as
   mid-wakeup, stranding a pending local reenqueue. If the scheduler was
   unloaded first, the stale request pointed into freed memory that the
   next scheduler dereferenced

 - ops.dequeue() ran with the source dispatch queue's lock held, so a
   scheduler iterating that queue from the callback deadlocked the CPU

 - Schedulers with their own CPU ID mapping had no way to learn a task's
   initial CPU mask and rebuilt it themselves, which went wrong across
   sub-scheduler enable and re-home. Pass it to ops.enable()

 - A bypass dispatch event counter missed the dispatches made by the
   end-of-dispatch fallback and under-reported

 - Selftests for the dequeue locking and initial mask changes

* tag 'sched_ext-for-7.3-rc4-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext:
  sched_ext: Count SCX_EV_SUB_BYPASS_DISPATCH in the dispatch fallback
  selftests/sched_ext: Check the cmask cid-form ops.enable() receives
  sched_ext: Pass the initial cmask to cid-form ops.enable()
  selftests/sched_ext: Test that ops.dequeue() can iterate the consumed DSQ
  sched_ext: Don't run ops.dequeue() with a DSQ lock held
  sched_ext: Derive SCX_RQ_IN_WAKEUP from the core enqueue flags
  sched_ext: Wait for SCX_OPSS_DISPATCHING before reenqueueing a task
This commit is contained in:
Linus Torvalds 2026-09-24 15:04:11 -07:00
commit ee9c669f9b
10 changed files with 671 additions and 72 deletions
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